The present invention relates to bumpers for passenger vehicles designed to reduce pedestrian injury upon impact, and more particularly relates to a bumper having an energy absorber optimized to provide a relatively soft initial impact and a xe2x80x9cthrowingxe2x80x9d force after initial impact to a pedestrian struck by the bumper.
Automotive bumper systems in the United States have been designed for resistance to damage at low and high vehicle speeds and for high-energy absorption at high impact speeds. Recently, pedestrian safety has begun to receive increasing attention. However, design of bumpers for pedestrian safety is complicated by several conflicting functional requirements. Obviously, the human body cannot withstand high-energy impacts nor sharp impacts without substantial damage to muscle and bone tissue. However, it is difficult to reduce the magnitude and rate of energy transfer from a bumper to a pedestrian upon impact, especially immediate transfer of energy from a xe2x80x9csharpxe2x80x9d impact, because vehicle bumpers are usually limited to a relatively short stroke by components behind the bumper, such as a radiator and other engine components, and also limited by other front-end components and supporting structure. This is especially true of smaller and more compact vehicles. Further, the bumpers must be made of strong materials in order to maintain their shape and appearance over time, and to provide their primary function of being a xe2x80x9cbumperxe2x80x9d for the vehicle to push away items and to prevent damage to the vehicle. The problems are further complicated by aerodynamic designs, where corners of the bumper system are swept and curved back into the vehicle fenders, which further limits bumpers strokes and the bumper""s ability to collapse or flex. Also, the problem is compounded by the fact that bumpers are at knee-height, such that pedestrian-related vehicular accidents often involve trauma to the pedestrian""s knees. Joints and exposed bones are particularly prone to injury upon impact.
Accordingly, a bumper system is desired solving the aforementioned problems and having the aforementioned advantages.
In one aspect of the present invention, a bumper system for a vehicle includes a beam adapted for attachment to a vehicle, and an energy absorber engaging a face of the beam. The energy absorber has a top horizontal section defined by a top wall and an upper-mid wall connected by an upper-front wall, and also has a bottom horizontal section defined by a bottom wall and a lower-mid wall connected by a lower-front wall, and still further has a middle horizontal section defined by a mid-front wall connecting the upper-mid wall and the lower-mid wall. The top and bottom horizontal sections include top and bottom front nose portions that extend forward of the mid-front wall and that define a horizontal channel therebetween in front of the mid-front wall. The front nose portions are configured to provide a first level of energy absorption during an initial impact stroke that collapses one or both of the front nose portions, with the top, middle, and bottom horizontal sections providing a higher second level of energy absorption during a continuing impact stroke that collapses the energy absorber against the face of the beam. A fascia covers the energy absorber and the beam. By this arrangement, during an initial front impact stroke, the top and bottom front nose portions provide a relatively low-energy absorption that xe2x80x9ccatchesxe2x80x9d an impacted object such as a knee of a human being, and then during a further continuing impact stroke, the top, middle, and bottom horizontal sections crush to provide an increased energy absorption.
In another aspect of the present invention, a bumper system for a vehicle includes a beam adapted for attachment to a vehicle and having a longitudinal curvature that, when viewed from above in a vehicle-mounted position, is shaped to match an aerodynamic curvilinear shape of a front of the vehicle. The bumper system further includes an energy absorber engaging a face of the beam. The energy absorber has a top horizontal section defined by a top wall and an upper-mid wall connected by an upper-front wall, and has a bottom horizontal section defined by a bottom wall and a lower-mid wall connected by a lower-front wall, such that the top and bottom horizontal sections including top and bottom front nose portions that extend forwardly. The top and bottom nose portions each are semi-rigid but are collapsible with a parallelogram motion that shifts one or both of the top and bottom front walls vertically, such that horizontal impact forces are converted at least in part to a vertical force upon receiving a horizontal frontal impact during an initial stroke of the frontal impact. By this arrangement, during a first part of the frontal impact, the top and bottom front nose portions provide a relatively low-energy absorption that xe2x80x9ccatchesxe2x80x9d an impacted object such as a knee of a human being, and then during a further continuing impact stroke, the top and bottom horizontal sections crush to provide an increased energy absorption.
In yet another aspect of the present invention, a bumper system for a vehicle includes a beam adapted for attachment to a vehicle and having a curvilinear longitudinal shape when viewed from above in a vehicle-mounted position, the beam including mounts positioned at ends of the beam. An energy absorber engages a face of the beam. The energy absorber has a middle section engaging the face and further has end sections that extend outwardly from the middle section and at least partially around the associated ends of the beam. The end sections each have an enlarged free end portion and a transition portion connecting the free end portion to an end of the middle section. Each of the transition portions of the end sections of the energy absorber, during a first part of a bumper stroke caused by a corner impact, are constructed to provide a relatively low-energy absorption and further are configured to torsionally crush so that the enlarged free end portion swings rearward and xe2x80x9ccatchesxe2x80x9d an impacted object such as a knee of a human being, and then during a further continuing part of the bumper stroke, the transition portion provides increased energy absorption and counteractive forces such that the free end portion pushes the impacted object away both due to lateral resistive forces developed in the energy absorber non parallel a line of impact and also due to sliding of the impacted object along an inclined surface of the free end portion.
In still another aspect of the present invention, a method comprises steps of constructing a bumper system including a stiff beam, and an energy absorber on a face of the beam. The energy absorber has top, middle, and bottom sections, with the top and bottom sections defining nose portions that extend forward of the middle section. The nose sections define a space therebetween in front of the middle section, the top and bottom nose sections being constructed to deflect with a parallelogram motion upon impact and that shift at least one of the nose portions vertically with a parallelogram motion in response to an impact directed horizontally against a front of the bumper system, whereby energy directed against a knee of an impacted person is converted into a throwing force that directs the person in a direction generally perpendicular to the line of impact and away from the vehicle bumper system.
The objects of the present invention include providing a bumper system adapted to initially xe2x80x9ccatchxe2x80x9d a person during an initial phase of impact, with less energy and forces being transmitted to the person and/or the forces being transmitted at a slower rate during the initial phase, and hence less injury being likely. The objects further include re-orienting the impact forces transmitted to the person from a line parallel the direction of impact to a direction upward or downward (in the case of a front impact) or laterally (in the case of a corner impact). By these actions, the impacted person is initially xe2x80x9ccaughtxe2x80x9d and then xe2x80x9cthrownxe2x80x9d in a direction away from the line of impact, thus reducing injury and also reducing damage to the vehicle bumper system.